Reflective-type mask blank for EUV lithography

Abstract

A reflective mask blank for EUV lithography including a substrate having a front surface and a rear surface, a reflective layer formed over the front surface of the substrate, an absorbing layer formed over the reflective layer, and a chucking layer formed on the rear surface of the substrate and positioned to chuck the substrate to an electrostatic chuck. The substrate has a non-conducting portion which eliminates electrical conduction between the reflective layer and the chucking layer and electrical conduction between the absorbing layer and the chucking layer, and the non-conducting portion is formed by forming a portion of the substrate covered with one or more covering members and preventing formation of the reflective layer and the absorbing layer.

1. A reflective mask blank for EUV lithography, comprising:
 a substrate having a front surface and a rear surface; 
 a reflective layer formed over the front surface of the substrate; 
 an absorbing layer formed over the reflective layer; and 
 a chucking layer formed on the rear surface of the substrate and positioned to chuck the substrate to an electrostatic chuck, 
 wherein the substrate has a non-conducting portion which eliminates electrical conduction between the reflective layer and the chucking layer and electrical conduction between the absorbing layer and the chucking layer, and the non-conducting portion is formed by forming a portion of the substrate covered with at least one covering member and preventing formation of the reflective layer and the absorbing layer such that the non-conducting portion provides the resistance value of 1 MΩ or above between the reflective layer and the chucking layer and the resistance value of 1 MΩ or above between the absorbing layer and the chucking layer. 
 
     
     
       2. The reflective mask blank according to  claim 1 , wherein the resistance value between the reflective layer and the chucking layer and the resistance value between the absorbing layer and the chucking layer are 5 MΩ or above. 
     
     
       3. The reflective mask blank according to  claim 1 , wherein the non-conducting portion is formed on the rear surface and positioned in a region beginning from edges of the substrate and extending in a width of 2 mm or above measured from the edges. 
     
     
       4. The reflective mask blank according to  claim 1 , wherein the chucking layer is formed in a region which has a smaller area than a contact area of the electrostatic chuck with the substrate, when the substrate is supported by the electrostatic chuck. 
     
     
       5. The reflective mask blank according to  claim 1 , wherein the non-conducting portion is formed on the front surface of the substrate. 
     
     
       6. The reflective mask blank according to  claim 5 , wherein the non-conducting portion is formed from edges of the substrate and extends in a width of 1 mm or above measured from the edges. 
     
     
       7. The reflective mask blank according to  claim 1 , wherein the reflective layer and the absorbing layer are formed in a square shape. 
     
     
       8. The reflective mask blank according to  claim 1 , wherein the non-conducting portion is formed on a lateral surface of the substrate. 
     
     
       9. A reflective mask for EUV lithography, fabricated by patterning the reflective mask blank defined in  claim 1 . 
     
     
       10. The reflective mask blank according to  claim 1 , wherein the substrate comprises SiO 2 —TiO 2  glass, and the SiO 2 —TiO 2  glass has one of a hydrogen molecule content of less than 5×10 17  molecules/cm 3  and an OH group content of 600 wt.ppm or below. 
     
     
       11. The reflective mask blank according to  claim 1 , further comprising a low-reflective layer on the absorbing layer, wherein the non-conductive portion eliminates electrical conduction between the low-reflective layer and the chucking layer. 
     
     
       12. The reflective mask blank according to  claim 1 , wherein the reflective layer is formed by depositing Si films and Mo films in from 30 to 50 cycles, and the reflective layer has a total thickness of from 200 to 400 nm. 
     
     
       13. The reflective mask blank according to  claim 1 , wherein the reflective layer has a capping layer formed as a top layer thereof. 
     
     
       14. The reflective mask blank according to  claim 1 , wherein the chucking layer comprises at least one metal material selected from the group consisting of Cr, Ni, Ti, Ta, Mo, Si and W. 
     
     
       15. The reflective mask blank according to  claim 1 , wherein the absorbing layer comprises Cr, Ta or a nitride thereof. 
     
     
       16. The reflective mask blank according to  claim 1 , further comprising an intermediate layer interposed between the reflective layer and the absorbing layer, wherein the non-conductive portion eliminates electrical conduction between the intermediate layer and the chucking layer. 
     
     
       17. The reflective mask blank according to  claim 1 , wherein the reflective layer includes a capping layer which prevents a surface of the reflective layer from being oxidized. 
     
     
       18. A method for manufacturing a reflective mask blank for EUV lithography, comprising:
 providing a substrate having a front surface and a rear surface; 
 covering a portion of the substrate with a first covering member which prevents formation of a reflective layer; 
 forming a reflective layer over the front surface of the substrate such that the portion covered with the first covering member forms a non-conducting portion which provides the resistance value of 1 MΩ or above between the reflective layer and a chucking layer; 
 forming an absorbing layer over the reflective layer such that the non-conducting portion provides the resistance value of 1 MΩ or above between the absorbing layer and the chucking layer by forming the portion covered with at least one of the first covering member and a second covering member and preventing formation of the absorbing layer; and 
 forming the chucking layer on the rear surface of the substrate such that the chucking layer is positioned to chuck the substrate to an electrostatic chuck. 
 
     
     
       19. The method for manufacturing a reflective mask blank for EUV lithography according to  claim 18 , wherein the forming of the reflective layer comprises forming a reflective layer including a capping layer which prevents a surface of the reflective layer from being oxidized. 
     
     
       20. The method for manufacturing a reflective mask blank for EUV lithography according to  claim 18 , further comprising forming an intermediate layer on the reflective layer, wherein the non-conductive portion eliminates electrical conduction between the intermediate layer and the chucking layer. 
     
     
       21. The method for manufacturing a reflective mask blank for EUV lithography according to  claim 18 , further comprising forming a low-reflective layer on the absorbing layer, wherein the non-conductive portion eliminates electrical conduction between the low-reflective layer and the chucking layer. 
     
     
       22. The method for manufacturing a reflective mask blank for EUV lithography according to  claim 18 , wherein the forming of the chucking layer is carried out after the forming of the reflective layer. 
     
     
       23. The method for manufacturing a reflective mask blank for EUV lithography according to  claim 18 , wherein the covering comprises covering the portion of the substrate with the first covering member comprising one of a photosensitive resist and a polyimide tape. 
     
     
       24. The method for manufacturing a reflective mask blank for EUV lithography according to  claim 18 , wherein the forming of the chucking layer is carried out before the forming of the reflective layer.